The module option makes it possible for the user to provide
their own callback module. The functions receive_message/4 or
process_received_message/4 of this module is called when a new
message is received (which one depends on the size of the message;
small - receive_message, large - process_received_message).
Default value is megaco.

Sends a message on a socket. The send handle is obtained by
megaco_udp:create_send_handle/3. Increments the NumOutMessages
and NumOutOctets counters if message successfully sent. In case
of a failure to send, the NumErrors counter is not
incremented. This is done elsewhere in the megaco app.